In the use of brine evaporators for the disposal of wastewaters and the reliance on seeded slurry brine recycle for scale control, scaling problems have been reported with the addition of conventional scale inhibitors, i.e., polyphosphates and polyacrylates; such scaling requires frequent and costly interruptions for descaling. Such descaling is often needed on about a 3 to 6 month cycle, with chemicals or by hydroblasting the scale from evaporator surfaces, with a reduction of evaporator productivity rates to about 60% of design capacity.
Brine concentrators take cooling tower blowdown (and other high TDS, TSS) waste, and concentrate this waste into solid waste material that can be disposed of in landfills. As a part of a zero discharge strategy, this apparatus is used when plants do not wish to or cannot discharge waste water into sewer systems.
The brine concentrator uses a vertical heat exchanger (condenser) to heat the waste water entering the process. This waste water is heated, turned into steam, with the water evaporating off being condensed as pure water used for boiler feed water make up. The brine residual solution that results is condensed in the base of the unit and removed as a highly concentrated slurry that is filter pressed and removed from the plant as solid waste.
The brine concentrator has a pressure indicator on the condenser, which displays whether it is being fouled by the concentrated brine residual by-products. These are typically dominated by calcium carbonate and calcium phosphate adhering to the condenser tube surfaces. At start up, the condenser typically has a back pressure of about 3 to 4 psi. As it fouls, the condenser has an increase of pressure to 5-6 psi, when it may then be shut down and cleaned.
The present invention has particular applicability at high temperatures (including those at or above the boiling point for water) and briny conditions where retrograde soluble salts such as calcium carbonate, calcium phosphate, etc. can be considered as potential foulants. Any area where high temperature and high solids loading (including brine and/or supersaturated conditions) where mineral scale foulants of this nature can occur will have applicability for the present invention. These include brine concentrators, evaporators, down-hole steam injection and recovery used in the geothermal power industry, and steam injection and recovery used in oil production and exploration.